Feed mechanism for rolling mill of the pilger type

ABSTRACT

In a feed mechanism for pilger rolling mills, having a mandrel rod coupled to a piston of a liquid brake, cooperating with a brake chamber. The compressed liquid in the chamber acts upon one side of a differential piston acted upon on its other side by a pressure force that persists beyond the instant of reversal of the mandrel rod.

United States Patent Bellmann [4 1 May 16, 1972 [54] F G [56] ReferencesCited MILL OF THE PILGER TYPE UNITED STATES PATENTS [72] Imam" BellmanRatmgen Germany 869,282 10/1907 Winter ..72/252 [73] Assignee: MannesmanAktiengesellschaft, Dussel- 1 1,041,661 10/1912 Nowak.... ...188/272dorf, Germany 1,122,013 12/1914 Ludwig ..72/252 [22] Filed: 1970 PrimaryExaminerLowe1l A. Larson [21] Appl. No.: 68,669 Att0rneySmyth, Roston &Pavitt and Ralf H. Siegemund [57] ABSTRACT [30] Foreign ApplicationPriority Data In a feed mechanism for pilger rolling mills, having amandrel Sept. 10, 1969 Germany ..P 19 46 798.2 rod coupled to a pistonof a liquid brake, cooperating with a brake chamber. The compressedliquid in the chamber acts [52] US. Cl ..72/445, 72/189, 72/252 upon onei f a differential piston acted upon on i other [51] Int. Cl ..BZlb25/02 Side by a pressure force that persists beyond the instant of [58]Field of Search ..72/189, 437, 445, 214, 252; reversal f h mandrelPar/Wall Tami/Mr 6 Claims, 1 Drawing Figure FEED MECHANISM FOR ROLLINGMILL OF THE PILGER TYPE The present invention relates to the feedmechanism for a rolling mill of the pilger type. More particularly, theinvention relates to the construction of a liquid brake included in thefeed mechanism of a pilger type rolling mill. The feed mechanism in sucha mill has the task of returning the work piece, i.e. the hollow bloomor billet, to a starting position, after disengagement from the pilgerrolls at the end of a rolling stroke or step. The next rolling stroke,of course, works another section of the same billet. The entire rollingprocess involves several alternating rolling and return strokes.

The brake in this device is to brake the return motion of the feedmechanism to obtain a controlled stop. Basically, the return of the feedmechanism to the starting position for the next rolling step is anunproductive operation and should be carried out in the shortestpossible time. Generally, it is deemed necessary that the feedmechanism, together with the billet, is at rest at the beginning of thenext roll cycle. Investigations on pilger type rolling mills have led tothe belief and conclusion that the acceleration of the feed mechanism bymeans of the rolls, as they rotate at a particular working speed, isresponsible for progressively accumulating torsional distortion in thedrive shafts or spindles and in the respective coupling and clutchelements. This cumulative distortion is deemed responsible for frequentbreakage of such parts. Thus, excessive loading of the rolls and of itsdrive elements at the beginning of a roll stroke or cycle is to beavoided.

The present invention is based on the principle that, prior toengagement of the billet by the rolls, the feed mechanism is to beaccelerated so as to assume, at least approximately, a linear speed thatcorresponds to the peripheral speed of the rolls at the point ofengagement. The so-called spring feed mechanism, as used in the past,have attempted this type of approach, but they were operated withoutdamping and that, in turn, led to vibrations within the feed mechanism,severely disturbing the entire operation.

The feed mechanism usually has a pneumatically operated piston andcylinder arrangement to provide for the return motion of mandrel andbillet. Some of the known feed mechanism are provided with air brakes,others employ liquid brakes. In the liquid brakes the piston has a frontend that enters a funnel-shaped brake cylinder filled with brakingfluid. Braking fluid is displaced, to leave the-brake chamber, e.g.,through a ring-gap between piston and chamber wall. Altematively, thebrake cylinder is provided with a bore governed by a pressure limitingvalve, to control bleeding ofi displaced braking fluid into a reservoir.In either case, kinetic energy of the feed mechanism is destroyed duringbraking. Particularly, kinetic energy is not stored for purposes ofaccelerating the equipment in opposite direction. The knownconstructions are not capable of providing for such storage.

Air brakes operate in that the feed mechanism compresses air during itsreturn stroke. The compression brakes the masses but the pressure islimited by means of the safety valve. For proper adjustment of the valvethe feed mechanism does, in fact, stop in the proper position at the endof the return stroke.

The present invention intends to improve particularly a feed mechanismfor a rolling mill of the pilger type and, as stated, refersparticularly to improvement of the liquid brake for such a feedmechanism. In addition, it may be assumed conveniently that the feedmechanism is pneumatically operated. The liquid brake is comprised of abraking piston and of a funnel-shaped braking cylinder with an exitopening for escape of displaced liquid during braking. It is unimportantfor practicing the invention whether or not the funnel-shaped brakingchamber is widened for establishing a ring-gap along the piston orwhether the braking funnel merges into a cylindrical portion, so thatthe braking chamber piston is sealed by the piston. However, the amountof liquid that is pennitted to escape at all from the brake cylinder inthis conventional manner should be limited as liquid displacement isutilized otherwise.

it is a particular feature of the invention that the braking chamber isconnected to act on the small surface of a freely displaceable,differential piston. The differential piston has a larger, low pressuresurface, acted upon by a counter or balancing force which is maintaineduntil the rolls re-engage the billet for the next rolling stroke. Thecombination of a balancing differential piston with a liquid brake incommunication'therewith, establishes a strongly damped system; themasses can be accelerated by operation of the counter force as actingupon the differential piston, but only once per rolling.

cycle stroke, the acceleration being effective opposite to the directionof motion during the return stroke and braking. The equipment will notoscillate about a starting position of the mandrel-piston arrangement.

The counter force, as referred to above, may be exerted upon thedifferential piston by a particular quantity of air which is containedin the auxiliary cylinder. This particular quantity of airis compressedduring braking, but expands during acceleration of the feed mechanism inthe reverse and moves the differential piston accordingly. It should benoted that difierential pressure piston is displaced by the relativelyincompressible liquid in the braking chamberacting on the small surfaceof the differential piston, while the relatively highly compressible airon the other, low pressure side of the differential piston, will besufficiently compressed to set up a reversely-accelerating force uponexpansion.

Alternatively, the counter force does not have to be buildup duringbraking of the feed mechanism but may be applied externally. Forexample, the auxiliary piston chamber is connected to the particularsource of air pressure source that feeds the air cylinder of the feedmechanism for obtaining the return stroke thereof. Practicing theinvention in this manner was found to be of particular advantage as thecounter force remains constant during braking as well as duringacceleration of the feed mechanism in the reverse so that, in fact, thereversal of motion can take place in the shortest possible time.

The stroke of the differential piston may be limited so that theduration of effectiveness of the counter force is limited accordingly.For example, after the differential piston has reversed, it may soonengage a cross wall, stopper plate or the like within the differentialpiston cylinder, so as to terminate further acceleration for the mandrelrod. Thus, a definitely ascertainable quantity of stored energy isavailable due to the particular construction in accordance with thepresent invention, which energy is available particularly foraccelerating the feed mechanism in the reverse so that the rolls engagethe billet on the mandrel when moving in the samedirection. Theoperation can, therefor, readily be analyzed; fast operating servo valvemechanism or the like are not needed.

It should be pointed out that a particular starting position forthebillet, in which the feed mechanism is at rest at the beginning ofthe next rolling stroke, is not really established. The feed mechanismmerely halts momentarily upon reversal of motion because the counterforce in the brake persists to obtain instantaneous reversal of motionof the mandrel and reacceleration, unidirectional with the motion of therolls.

Means are provided to indicate engagement of the billet by the rollsand/or which indicate the position of the billet relative to the phaseangle of the rolls. Actually, the engagement is a particular relativephase position of rolls and billet. These means may not only includetransducers to ascertain and to provide particular representation ofinterest, but they also may provide control signals which operate thefeed mechanism or the carriage on which the feed mechanism is advanced,so as to control (in time) the point where the rolls engage the movingbillet. In other words, the phase of return motion of the billet iscontrolled so that for the given parameters, such as speed of the rolls,the span to the pilger rolled in the next rolling stroke is determined,through appropriate phase timing of the reengagement of the billet bythe rolls.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention,

the objects and features of the invention and further objects, featuresand advantages thereof will be better understood from the followingdescription taken in connection with the accompanying drawings in which:

The FIGURE is a crosssection through the braking and control mechanismfor the feed equipment in a pilger rolling mill.

The stand of the pilger rolling mill is generally denoted with referencenumeral 3. Reference No. 4 denotes the operating rod for the feedmechanism which is linked to the mandrel supporting the hollow bloom orbillet to be pilger rolled. Though, frequently rod 4 is constructed tobe disconnectible from the mandrel, it will be termed mandrel rod, as itis connected to mandrel and billet thereon during the particularoperating phases of the invention. The mandrel as well as components 3and 4 pertain to known types of feed mechanism that do not requireelaboration. The same is true as to billet and rolls in the stand 3.

A cylinder 1 is part of the feed mechanism carriage, and is disposed forreceiving a piston 2 reciprocating in a piston chamber thereof. Duringpilger rolling, and here particularly during a rolling stroke, piston 2moves to the right in the drawing, whereas the return motion of the feedmechanism is carried out to the left,towards rolling stand 3. A carriageadvance is. superimposed upon the return motion of the feed mechanism.

The motion to the right is imposed upon elements 2 and 4 by means of therotating pilger rolls as acting upon the billet and, thereby, upon thefeed mechanism for displacing rod 4 to the right. The axles of thepilger rolls, of course, remain stationary in relation to the system.The return motion for the feed mechanism to the left has piston 2 moveunder the influence of air pressure acting in cylinder chamber 5connected to a source 18 of air pressure via an air conduit 7. Thesource 18 of pressure may be controlled to pressurize chamber 5 forobtaining the return motion of piston 2 (and of the billet afterdisengagement from the rolls). During a rolling stroke, pipe 7 isshut-ofi' from source 18. Reference numeral 17 denotes the twist spindleof the feed mechanism.

As stated, during the return stroke air pressure in chamber 5 forcespiston 2 to the left. In order to provide braking during the return ofthe feed mechanism a water brake is provided comprised of afunnel-shaped braking cylinder 6 coacting with a head 16 of pistonhaving configuration of a trunk-acted cone. The funnel-shaped brakecylinder 6 is provided with one or more exit openings 9 whichcommunicate with an auxiliary cylinder 10.

A differential piston 11 reciprocates freely within cylinder 10. Thedifferential piston l 1 has a first, relatively small piston surface 12,acted upon by the braking fluid as is permitted to enter auxiliarypiston chamber 10 via duct or ducts 9 upon displacement from chamber 6by the piston 2. The oppositely effective, relatively large secondpiston surface 13 of differential piston 11 is acted upon by pressure ofair in auxiliary chamber 10'. A cross wall 20 limits the stroke ofdifferential piston 11 when piston 2 is moved to the right by operationof the air pressure in chamber 10" as acting upon piston surface 13 forreversal of motion of mandrel rod 4 and of other parts of the feedmechanism. Air pressure for chamber 10" is provided by the same source18, via a pipe 7 An adjustable valve 14 is provided in a pipeline 15,which connects braking chamber 6 with a fluid tank such as waterreservoir 8. The dashed line in tank 8 denotes the water level therein.Valve 14 is used only during the first few operating strokes uponrolling a new hollow billet. The valve is constructed so that brakingfluid, i.e., water, can be sucked from the tank 8 into the brakingchamber, the suction being produced by piston 2. During the returnstroke the braking force is limited accordingly, Flow of braking fluidthrough pipe 15 is completely blocked by means of valve 14 duringsubsequent pilger steps, so that the braking force is determinedexclusively by the balance of forces acting upon differential piston 11.

As it can be seen, during regular operation piston 2 is moved to theleft to return the billet, mandrel and mandrel rod for engagement of thebillet with the pilger rolls in the next rolling stroke. The returnmotion is induced by opening chamber 5 to air pressure from source 18(there may be a valve in pipe 7). The motion is impeded as piston head16 enters chamber 6 and tends to compress the water in chamber 6,thereby causing the water to be displaced. The displaced water shiftspiston 11 so that balance with pressure force acting on piston surface13 is maintained. As piston 2 slows down and stops, pressure force, asacting on 13, persists, so that piston 2 reverses and accelerates themandrel rod 4 so that upon reengagement of the billet by the rolls theymove at approximately similar speed.

Chamber -5 may have to be vented and line 7 is turned off A duringbraking to tenninate the pneumatic driving of piston 2 (to the left)prior to inducement of reversal by operation of the differential piston.Pressure on surface 13 should persist as that persistence induces thereversal and should remain operative in this manner at least untilpiston plate having surface 13 stops and sits on cross wall 20. Also,during this acceleration phase, as piston 2 moves to the right, thepiston should not have to work against operating pressure in chamber 5.Pipes 7 and 7' may be governed by separate valves so that the operatingair pressure acts on differential piston 11 longer than on piston 2.Actually, chamber 10" ofthe differential piston-does not have to bedisconnected from source 18 at any time as wall 20 restricts the motionof piston 11. Thus, a valve may not be needed in line 7 Transducers 22are provided to ascertain the relative position of rolls and billet,possibly ascertaining also the instant of engagement. The output signalsmay be used to control, for example, the timing of actuating the valvecontrol for pressurizing chamber 5 and/or to control a carriage drive 21that advances the feed mechanism as a whole. Considering, that the rollsrotate at constant speed, the relative phase of feed mechanism, carriageadvance and return of rod 4 etc. on the one hand, and of the rolls onthe other hand, determines the point of re-engagement between rolls andbillet. That point, in turn, determines the span or axial section of thebillet to be rolled next. Thus, upon properly phasing the return motionof feed mechanism and billet, re-engagement of rolls and billet can becarried out while the billet is in motion.

A second embodiment can be regarded as being included in the figure.Assuming pipe 7 is eliminated and chamber 10" is closed, that chamber isan air cushion that is compressed to some extent during braking, butexpands as soon as piston 2 has stopped.

The invention is not limited to the embodiments described above but allchanges and modifications thereof not constituting departures from thespirit and scope of the invention are intended to be included.

I claim 1. In a feed mechanism for rolling mills of the pilger variety,which includes a liquid brake and an air cylinder for operating movableparts of the feed mechanism, e.g., mandrel of the pilger roll, the brakeincluding a piston connected to the mandrel supporting the billet to bepilger rolled, the piston cooperating with a funnel-shaped, water filledbrake chamber, thereby establishing pressure in the chamber, theimprovement comprising:

first means defining an auxiliary cylinder;

a differential piston disposed for reciprocation in the cylinder andhaving first and second oppositely effective piston surfaces;

second means for connecting the brake chamber to the cylinder for thepressure of the liquid in the brake chamber to act on the first pistonsurface of the differential piston;

third means for providing a pressure force to act on the second largerpiston surface; and

fourth means connected for operating the third means for obtaining thepressure force and sustaining the latter force until the pilger rollsre-engage the billet, so that the piston is accelerated in the reverseprior to the return cycle of the feed mechanism.

2. In a feed mechanism as in claim 1, the second differential pistonsurface being larger than the first surface, the pressure force beingprovided by air acting on the second surface.

37 In a feed mechanism as in claim 2, the auxiliary cylinder beingclosed, the air in the resulting chamber being compressed by operationof the second surface of the difierential piston, the compressed airproviding the second force.

4. In a feed mechanism as in claim 2, there being a source of pressurefor operating the air cylinder, said source connected to said auxiliarypiston for the pressure to act on the second surface of the differentialpiston.

5. In a feed mechanism as in claim 1, there being means for limiting thestroke of the difierential piston.

6. In a feed mechanism as in claim 1, there being means to ascertainrelative position of the rolls and billet to provide control of thephase of reversal of motion of the piston relative to the instant ofre-engagement of rolls and billet, after a return stroke.

1. In a feed mechanism for rolling mills of the pilger variety, whichincludes a liquid brake and an air cylinder for operating movable partsof the feed mechanism, e.g., mandrel of the pilger roll, the brakeincluding a piston connected to the mandrel supporting the billet to bepilger rolled, the piston cooperating with a funnel-shaped, water filledbrake chamber, thereby establishing pressure in the chamber, theimprovement comprising: first means defining an auxiliary cylinder; adifferential piston disposed for reciprocation in the cylinder andhaving first and second oppositely effective piston surfaces; secondmeans for connecting the brake chamber to the cylinder for the pressureof the liquid in the brake chamber to act on the first piston surface ofthe differential piston; third means for providing a pressure force toact on the second larger piston surface; and fourth means connected foroperating the third means for obtaining the pressure force andsustaining the latter force until the pilger rolls re-engage the billet,so that the piston is accelerated in the reverse prior to the returncycle of the feed mechanism.
 2. In a feed mechanism as in claim 1, thesecond differential piston surface being larger than the first surface,the pressure force being provided by air acting on the second surface.3. In a feed mechanism as in claim 2, the auxiliary cylinder beingclosed, the air in the resulting chamber being compressed by operationof the second surface of the differential piston, the compressed airproviding the second force.
 4. In a feed mechanism as in claim 2, therebeing a source of pressure for operating the air cylinder, said sourceconnected to said auxiliary piston for the pressure to act on the secondsurface of the differential piston.
 5. In a feed mechanism as in claim1, there being means for limiting the stroke of the differential piston.6. In a feed mechanism as in claim 1, there being means to ascertainrelative position of the rolls and billet to provide control of thephase of reversal of motion of the piston relative to the instant ofre-engagement of rolls and billet, after a return stroke.